Character generator for crt display having parallel delay lines



Feb 9. 1955I AMAcovsKrl CHA-RAGTER GENERATOR Foa` CRT: DISPLAY HAVING PARALLEL DELAY' LINESy 2 Sheets-Sheet 1 INVENTOR.

Feb; 9, 1965 A. MAcovsKl CHARACTER GENERAmRz Foa om DISPLAY HAVING PARALLEL DELAY LINES 2. Sheatsr-Sheetl 2..

Filed Dec-y l. 1951 uw .mm

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14745597 mm1/Sel United States Patent O M 3 169 24) CHARACTER GENERTR FR fCR'i` BISPLAY HAVNG PARALLEL DELAY LHJES Albert Maccvslri, Pain Alto, Calif., assigner to Stanford Research Institute, Palo Atto, Calif., a corporation of California Filed Dec. i, 1%1, Ser. No. 156,3@Y 5 Claims. (Ci. 346-324) This invention relates to electronic apparatus for generating characier-representante signals and, more particularly, to an improvement in circuits for generating signals which may be displayed as characters.

An object of this invention is the provision of a simple circuit arrangement for providing signals which are easily displayable as characters.

Another object of this invention is the provision of an inexpensive character-signal generator.

Yet another object of the present invention is the provision of a useful character-signal-generator system.

These and other objects of the present invention may be achieved in a circuit arrangement wherein there is a delay line, preferably consisting of a plurality of sections of a delay line connected in series with one another. A pulse source is provided for applying a pulse to one end of the connected-together delay-line sections, and the output end of these delay lines is connected to ground through an impedance-matching load. A winding, which may be designated as a sense winding, is inductively coupled to the various delay-line sections at a number of different locations which are spaced along said delay line so that a pulse, which travels through the delay-line sections, induces a voltage in the sense winding at each one of the coupling locations. The pattern of coupling of the sense Winding to the delay line is such as to provide a sequence of pulses spaced in a manner so that when applied, for example, to intensifying the beam of an otherwise blanked cathode-ray tube, wherein the beam is properly deiiected, such cathode-ray tube will display an alpha-numeric character, as determined by the pattern of the coupling of the sense winding to the plurality of delay-line sections.

A dilerent group of delay-line sections may be employed in combination with a different sense-winding pattern for each different alpha-numeric character desired to be represented. Alternatively, as many ditte-rent sense windings as are feasible may be coupled on a single group of delay-line sections. Provision is then made for selectively connecting to the display device a desired one of the sense windings. Selection of a sense winding may be made, for example, by digital-selecting signals from a source.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, both as to its organization and method or" operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:

FIGURE 1 is a circuit diagram of an embodiment of the invention; and

FIGURE 2 is a circuit diagram of an alternative arrangement for the embodiment of the invention.

Reference is now made to FIGURE l of the drawings, wherein the embodiment of the invention is shown. liffectively, there is shown in the drawing a plurality of character-signal-generating circuits, which are connected to character-selection logic circuits, output oi' which is connected to a character-display device. ln accordance with this invention, the character-signal generating circuits may comprise a plurality of distributed delay-line sections 10, l2, 14, l, 13, with a sensing winding 24 coupled thereon. By way of illustration, the coupling of the sensing winding is such as to provide signals repreihzd Patented Fel). 9, l

senting the character S. These delay lines are connected in series. They are preferably disposedor arranged as a grid, since this enables a visual determination of the proposed coupling points of a sensing Winding to the delay lines. One end of the serial-connected delay lines is connected to a pulse source 2t). The other end of the serial-connected delay lines is connected through a matching characteristic impedance to ground. The delay lines are shown as being disposed parallel and adjacent to one another for convenience and compactness, although this need not be the case.

A sense winding 24 is coupled to the delay line sections iti through 18. The simplest explanation of the method employed for coupling the sense winding to the delay-line sections is to indicate that, when the delay lines are disposed as a grid, the sense winding is given the shape of the character for which signals are desired. The sense winding may be considered as being physically laid over the ve parallel delay-line sections .and being inductively coupled to each delay-line section at the location of a crossing therewith. Thus, as shown in the drawing, the letter S is represented by the sense Winding 24, and this sense winding is inductively coupled to the delay line section 19 at the three locations, respectively 24A, 245B, 24C, at which it crosses the delay-line section.

One end of the sense winding 24 is connected to ground; the other end of the sense Winding is connected to character-selection logic circuits, represented by a rectangle 26. Also connected to the character-selection logic circuits is another sense winding 28 (which provides signals representative of the character U) and 30 (which provides signals representative of the character F). It will be appreciated that as many sense windings as desired may be connected to the character-selection logic circuits. The character-Selection logic circuits may comprise any arrangement for selecting one out of'rnany inputs and connecting it to a single output. The selection may be made by signals such as digital signals from a character-selection signal source 28. The character-selection logic circuits may comprise, for example, a magneticcore switch wherein all but a desired one of the magnetic cores is biased to prevent signal translation. Or, the character-selection logic circuits may constitute a selector switch or a plurality of relay contacts, wherein only one of the relay contacts is closed in response to characterselection signals. Or, the character-selection logic circuits may constitute a diode-selection matrix. All these circuits are well known and are thoroughly described in published literature.

Also shown, by way of example, are arrangements of the sense windings, respectively 28, 30, for providing a signal train representing the character U and another for representing the character R The sense winding 23 is inductively coupled to the delay-line sections, respectively 19A, 12A, 14A, 16A, and 18A. The coupling of the sense Winding 28 to the delay-line sections 10A and 18A establishes the arms of the U, and the base of the U is established by the coupling of the sense winding to the delay-line sections 12A, 14A, and 16A.

The sense winding 3i! is inductively coupled to delayline sections 12B, 14B, 16B, and 18B. Signals for the vertical-bar portion of the letter F are derived by means of the coupling of the sense winding 40 on the delay-line section 12B. Signals representing the top horizontal-bar section of the letter F are denved by the portion of the sense winding which is inductively coupled to delay-line sections 12B, 14B, 16B, and 18B. Signals representative of the other horizontal-bar section of the letter F are generated by the inductively coupled portions of the sense winding 30 on the delay sections 12B, 14B, and 16B.

aleen-io 26 is applied to the brightness-control grid 42 of the cathode-ray display. device 44. The cathode-ray display device is normally operatedwith the cathode-ray beam biased oi by a bias source 46 which is connected to the cathode 48. A source of horizontal-deection signals Se are synchronized by pulses from the pulse source Ztl. A

Y source of vertical-detiection signals 52` are synchonized also by pulses from the pulse source Ztl.' The horizontaldeection signals and thevertical-deliection signals are respectively applied to the horizontaland vertical-de.- ecting electrodes of the cathode-ray tube 44. The

verticaland horizontal-deflection signal sources provide deliection signal outputs which provide a scanning raster on the cathode-ray tube face which resembles the grid .formed by the delay-line sections. The amplitude of a scanning raster is determined by lthe size of the display desired for each character. Similarly, the frequency of the deflection signal is determined by the delay of the delay-line sections, Aas well as their number.

In order to operate the invention, the pulse source 2@ is actuated to apply a Ipulse to the input tol all of the serial-connected delay-line sections. The horizontaland vertical-deection signal sources 5i), 52 start applying the deflection signals to the cathode-ray beam of the tube 44,`which is normally biased oli. Assuming that the letter vSV is selected by the character-selection logic circuits, in response to signals from the character-selection signal source 29, the sense winding 24 has induced therein a train of pulses as a resultof the passage of the pulse fromsource 20 through the delay-line sections 1t) through 18, kwhich are connected in series. Each time a voltage is induced in the sense winding 24 the cathode-ray beam of the cathode-ray tube 44 is unblanked, whereby the cathode-ray beam strikes .the screen of the cathode-ray tube. Now,fit the horizontal-deflection signals deflect the cathode-ray Vbeam houzontally over an interval re- `quired for the pulse applied to the delay-line sections through 13 to traverse fromone end to the other of these delay-line sections and if the vertical-deection signals make ve sweeps (corresponding to the tive delayline sections) foreach one of the horizontal-deflection signals, then it should be appreciated that there will be displayed on a cathode-ray tube face a pattern of bright spots which represent theletter S. The size of the letter S which is displayed is a function of the amplitude ofthe verticaland horizontal-deection signals.

It will be appreciated that a character generator of the type just described for providing signals representative of each character of the; alphabet may be readily constructed. The character-selection Alogic circuits 26 can be actuated by signals from the source 29 to select the sensing windings in a4 sequence so that intelligible words The verticaland horizontal-demay be spelled out. iiection signalsmay have their amplitudes adjusted so that these words are displaced on a line across the face of the cathode-ray tube, and by other techniques well known in the art, such as adding a voltage having a stairstep Y waveformV to the horizontal-deflection signals whereby the `cathode-ray tube face can display a plurality of lines K of words.

The circuit diagram shown in FIGURE 2 is for an :arrangement of the invention which shows how to obtain :a number of synchronizing pulses from the charactersignal generator for operating the display apparatus. This arrangement is preferred, since it minimizes the chances of the deflection circuits going out of phase with the generated signals. vThis is achieved by takingrsynchronizing signals from each delay-line section.

By way of illustration, a character generator for the letter L is shown. There are four delay-line sections 66, 62, 64, 66 employed, which are arranged in the form of a grid. A sensing winding 63 is shaped to form the letter L on the grid, anda coupling is made with a delay-line section at every intersection. One end of the irst 'delay-line section o@ is connected to a pulse source '70, the other end being connected through a characteristic impedance .72 to ground. A pulse amplifier, but preferably a blocking oscillator 7d, has its input connected to the end of the irst delay-line section and its output connected to one end of Vthe second delay-line section e2. Thus, when the blocking oscillator 74 has its input energized by the output of the rst delay line section, it applies an amplified pulse to the input to the second delay-line section.

The just-described arrangement for the inter-connection of the first two delay-line sections is repeated for the remaining delay-line sections. Each of the delayline sections 62, de, 66 has one of its ends terminated in a characteristic impedance, respectively 7d, 78, Se. A blocking oscillator 81, de respectively couples a preceding delay-line section to a succeeding delay-line section. Thus, a pulse applied from the pulse source to the first Vdelay-line section is successively renewed at each succeeding delai -line section.

Output from the pulse source 7), as before, is applied to the horizontal-detiection circuit S12 to provide a synchronizing signal. However, synchronizing signals `for the vertical-deflection circuits 83 are collected by a bus conductor Se, which is connected to an end of each of the delay-line sections through an isolating resistance, respectively 8S, 90, 92,94.

As previously explained, the output of the sensing winding o8 is applied through character-selection logic circuits S5 and a suitable amplitier 87 to the cathoderay tube Se, toV overcome the bias 9b applied thereto, which otherwise Vmaintains the cathode-ray beam biased oit. WithV the system described, each vertical-scanning line is initiated by a synchronizing pulse from each delayline section, thus minimizing any ypossibility of Vdrift or loss of phasing.

Instead of displaying the selected characters on the cathode-ray tube, it may be desirable to printout the characters whose signals are produced by the character generator. This may be accomplished by substituting, in place of the cathode-ray tube, an electrostatic-printing device, such as is shown and described in a patent to R. W. Crews and C. W. Barnes, Jr., No. 2,952,796, for Electrostatic Printing Tube. This device essentially comprises a cathode-ray tube having a grid of wires in the face thereof vover which the cathode-ray beam is deilected. Electrostatic writing paper is moved pastrthe face of the cathode-ray tube, so that line-byline writing thereon may be accomplished.

The delay-line sections i through 18 employed in the character-generator circuit are shown in the drawing as being arranged as a grid of parallel delay-line sections which are vertically disposed. Disposing the del lay-line sections so that the grid lines are horizontal or at some angle relative to the horizontal is still to be considered within the scope of thisjinvention, since the basic inventive principle is still used, namely, generating a train of character-representative signals from a sense winding inductively coupled at a plurality of predetermined locations to a delay line, to derive these signals from a pulse passing through the delay line. Also, using a single delay line, or one which is not disposed as a parallel grid of delay-line sections to which a sensing winding is coupled at a plurality of predetermined locations to derive character-representative signals from a Vpulse passing through the delay line, is to be considered l claim:

l. A character-signal generator comprising a plurality of delay-line sections connected in series with one another, a sensing winding inductively coupled to said plurality of delay-line sections at a plurality of locations in accordance with a predetermined pattern, said predetermined pattern being determined by disposing said delay-line sections in the form of a grid and disposing said sensing winding over said grid in the shape of a character for which signals are desired, and connecting said sensing winding to said delay-line sections at the locations established by the intersections of said sensing winding with said delay-line sections, and means for applying a pulse to one end of said delay-line sections, whereby signals are induced in said sensing Winding having a spacing determined by said coupling pattern.

2. An improved character-signal generator as recited in claim l wherein there are a plurality ot said sensing windings coupled to said delay-line sections in different predetermined patterns for generating different charactersignal trains, a character-display device, and means for selecting a desired one of said plurality of sensing windings for connecting to said character-display device for displaying signals induced therein.

3. A character generator comprising a plurality of groups of delay-line sections, each group of delay-line sections comprising a plurality of delay lines connected in series and arranged as a grid of parallel delay lines, a

plurality of sensing windings, a diierent one of said plu-- rality of sensing windings being inductively coupled to the delay-line sections in a diierent one of said groups of delay lines, each diierent sensing Winding being shaped as a diilerent predetermined character over a different one of said grids and being inductively coupled to the respective delay line sections forming said grid at locations at which intersections therebetween occur, means for applying a pulse to one end of all said delay-line sections, character-display means, and means for selecting a predetermined one of said sensing windings for connection to said character-display means.

4. The combination of a character signal generator and display device comprising a plurality of delay line sections connected in series with one another, a sensing winding inductively coupled to said plurality of delay line sections at a plurality of locations in accordance with a predetermined pattern, said predetermined pattern being determined by disposing said delay line sections in the form of a grid, disposing said sensing winding over said grid in the shape of a character for which signals are desired, and connecting said sensing winding to said delay line sections at the locations established by the intersections of said sensing winding with said delay line sections, means for applying a pulse to one end of said delay line sections whereby signals are induced in said sensing winding having a spacing determined by said coupling pattern, a cathode ray tube including a cathode ray beam and a screen, means for repetitively detlecting said cathode ray beam along a first coordinate over the interval required for a pulse to traverse one of said delay line sections, means for deecting said cathode ray beam along a second coordinate over the interval required for a pulse to traverse all of said delay line sections, means for biasing off said cathode ray beam, and means for applying the output signals of said sensing Winding to said cathode ray tube to override the eects of said means for biasing ot with said signals whereby the character determined by the pattern of the coupling of said sensing winding to said delay sections is displayed.

5 The combination of a character signal generator and display device comprising a plurality of groups or delay line sections, each group of delay line sections comprising a plurality of delay lines arranged as a grid of parallel delay line sections which are connected in series, a plurality of sensing windings, a different one o said plurality of sensing windings being inductively coupled to the delay line sections in a different one of said groups of delay lines, the manner of coupling being determined by shaping each dilerent sensing winding as a different predetermined character over a diiferent one of said grids of delay lines and inductively coupling to said delay lines at the locations at which each said sensing winding overlays the grid, the pattern of the coupling of each sensing winding being determined in accordance with a character for which representative signals are desired to be generated within said sensing Winding, means for applying a pulse to one end of all said delay line sections, a character display means, means for selecting a predetermined one of said sensing windings for connection to said character display means, said character display means including a cathode ray tube having a cathode ray beam and a screen, means for repetitively deflecting said cathode ray beam along a first coordinate over the interval required for a pulse to traverse one of said plurality of delay lines in a group, means for deflecting said cathode ray beam along a second coordinate over the interval required for a pulse to traverse all of the delay lines in a group, means for biasing ott said cathode ray beam, and means for applying the signal output of a selected one of said sensing windings to said cathode ray tube to override said means for biasing ott whereby the character determined by the pattern of the coupling of said sensing Winding to said selected delay line sections is displayed on said screen.

References Cited by the Examiner UNITED STATES PATENTS 2,540,560 2/51 Wheeler 340-354 X 2,710,958 6/55 Sallach 340-354 2,920,312 1/60 Gordon et al. S40-324.1 2,931,022 3/60 Triest 340-3241 2,973,509 2/61 Majerus et al. 340-345 3,103,658 9/63 Chiang V S40-324.1

NElL C. READ, Primary Examiner. 

1. A CHARACTER-SIGNAL GENERATOR COMPRISING A PLURALITY OF DELAY-LINE SECTIONS CONNECTED IN SERIES WITH ONE ANOTHER, A SENSING WINDING INDUCTIVELY COUPLED TO SAID PLURALITY TO DELAY-LINE SECTIONS AT A PLURALITY OF LOCATIONS IN ACCORDANCE WITH A PREDETERMINED PATTERN, SAID PREDETERMINED PATTERN BEING DETERMINED BY DISPOSING SAID DELAY-LINE SECTIONS IN THE FORM OF A GRID AND DISPOSING SAID SENSING WINDING OVER SAID GRID IN THE SHAPE OF A CHARACTER FOR WHICH SIGNALS ARE DESIRED, AND CONNECTING SAID SENSING WINDING TO SAID DELAY-LINE SECTIONS AT THE LOCATIONS ESTABLISHED BY THE INTERSECTIONS OF SAID SENSING WINDING WITH SAID DELAY-LINE SECTIONS, AND MEANS FOR APPLYING A PULSE TO ONE END OF SAID DELAY-LINE SECTIONS, WHEREBY SIGNALS ARE INDUCED IN SAID SENSING WINDING HAVING A SPACING DETERMINED BY SAID COUPLING PATTERN. 